The present application is related generally to the measurement and alignment of the axles of a trailer or semi-trailer configured to be coupled to a tow vehicle, and in particular, to a method for measuring the alignment of the axles of a single or multi-axle trailer or semi-trailer without the need to jack the trailer or semi-trailer off the ground, without the need to reposition sensors from one location to another, and without the need to separate the trailer or semi-trailer from the tow vehicle.
The measurement and alignment of the axles of a single or multi-axle trailer or semi-trailer is commonly a time consuming process, but one which is beneficial to optimize fuel economy, improve handling, and prevent excessive tire wear. Initially, the trailer or semi-trailer to be serviced is towed into the service or inspection facility by a tow vehicle, and positioned in service bay. The tow vehicle is uncoupled from the trailer or semi-trailer and moved away. For semi-trailers, this provides the service technicians with access to the kingpin or fifth wheel coupling from which the semi-trailer is towed by the tow vehicle. The kingpin or fifth wheel coupling is utilized to establish a reference location on the body or frame of the semi-trailer relative to which the semi-trailer axles can be measured and aligned, such as shown in U.S. Pat. No. 6,886,266 B2 to Kidd et al. and seen in FIG. 1. An ideal alignment scenario for a trailer or semi-trailer is one in which all of the trailer or semi-trailer wheels are parallel to one another and perpendicular to the centerline of the trailer or semi-trailer (i.e., when D1=D2 and D3=D4 as seen in FIG. 1). This is achieved, as shown in FIG. 2, by initially adjusting the thrust angle of one trailer or semi-trailer axle, and on a tandem-axle or multi-axle trailers or semi-trailers, subsequently adjusting the scrub angle between the initially adjusted axle and each remaining axle.
In order to utilize the kingpin or fifth wheel coupling to establish a reference location, a sensor bar or kingpin adapter is connected to, or aligned with, the kingpin or fifth wheel coupling at a longitudinally centered reference point. The reference point is generally horizontally perpendicular to the semi-trailer centerline. The opposite longitudinal ends of the sensor bar are configured to each receive and support an alignment sensor unit adjacent to a respective side of the semi-trailer. Each alignment sensor unit provides an observable reference point for additional sensor units initially mounted to the outer wheel assemblies on a first axle of the semi-trailer, from which the distance between the wheel-mounted sensor units and the kingpin or fifth wheel coupling reference point can be determined. Once the thrust angle of the first axle of the semi-trailer is measured and aligned relative to the kingpin reference point, the first pair of alignment sensor units is removed from the sensor bar or kingpin adapter, and for a tandem axle semi-trailer, mounted to a second axle of the semi-trailer. With the alignment sensor units mounted to the second axle of the semi-trailer, distances between the outermost wheels on the first and second axles are measured to determine the associated scrub angle. The associated scrub angle between the axles is then adjusted as necessary by altering the orientation of the second axle, bringing the tandem axles into parallel alignment within a required tolerance. For multi-axle semi-trailers having more than two axles, the alignment sensor units mounted to the second axle are removed and remounted on the next adjacent unaligned axle to acquiring measurements relative to the first axle, enabling necessary adjustments to the scrub angle between the axles to be made by altering the orientation of the new axle. The process is repeated for each unadjusted axle of the semi-trailer until all subsequent axles have been measured and aligned relative to the first axle to within specification tolerances.
Depending upon the type and configuration of the alignment sensor units being utilized on the trailer or semi-trailer, it may be necessary to elevate the wheels of individual axles off the ground and carry out a runout compensation procedure each time the sensors are mounted. Some runout compensation procedures require rotating a wheel about its axis while recording measurements with the installed alignment sensor at several different rotational positions. Hence, for a tandem or multi-axle trailer or semi-trailer, it may be necessary to elevate the trailer or semi-trailer axles two or more times, once to compensate the alignment sensors mounted to the first axle, and once each time a set of alignment are sensors remounted on an unadjusted axle. The process of elevating the trailer or semi-trailer and sequentially compensating sensors is time consuming, and may require specialized lifting equipment.
Accordingly, there is a need in the industry to improve the efficiency of trailer and semi-trailer axle measurement procedures, and in particular, a need to reduce the steps required to measure and adjust tandem or multi-axle trailers or semi-trailers.